Forest not required – indoor air quality and plants

Ever since modern offices have relied on air conditioning for ventilation, indoor air quality has been a contentious occupational issue from other people’s smells to thermal comfort to photocopier toner dust.

The prominence of air quality in offices as an OHS issue can be illustrated by a paragraph from the 1997  edition of Officewise, when cigarette smoke remained a real hazard.  No mention was made of plants.

Air in offices may be contaminated by several different
sources, including odours and micro-biological and
chemical contaminants. In an office environment, the
quality of the air is often controlled through an air
conditioning system. A building’s air conditioning
system may be considered as its lungs. The function
of such a system is to draw in outside air, filter, heat,
cool or humidify it and circulate it around the building.
The system expels a portion of the air to the outside
environment and replaces this expelled portion with
fresh or outside air.

“Air in offices may be contaminated by several different sources, including odours and micro-biological and chemical contaminants. In an office environment, the quality of the air is often controlled through an air conditioning system. A building’s air conditioning system may be considered as its lungs. The function of such a system is to draw in outside air, filter, heat, cool or humidify it and circulate it around the building. The system expels a portion of the air to the outside environment and replaces this expelled portion with fresh or outside air.”

The focus was (pre-green buildings) on mechanical ventilation but even in the 2006 edition there was no mention of the any benefits from indoor plants.

A haughty OHS response to these issues would be to just open a window and eliminate the hazards.  But the capacity to open office windows has not been available for several decades whether it is for the reasons of comfort or to eliminate the risk of people jumping through windows or for energy efficiency or security, is debatable.

Throughout the “closed environment decades” there have been plant advocates.  There have long been claims that plants are calming and increase productivity although some of the sick plants in some offices are evidence only of coffee dregs and in the 1980’s, cigarette butts.  Robin Mellon of the Green Building Council Australia puts the value of plants in the workplace context.

Finally there seems to be some evidence about the air filtration capacity of plants indoors.  According to a recent media statement from the University of Technology Sydney (via a company who supplies plants to offices), research has been undertaken that shows “that any plants can improve indoor air quality and the size of the pot or plant does not matter above 200mm. Adjunct Professor Margaret Burchett says

“We have found that a plant in a 200mm pot is as effective as one in a 250mm or 300mm in removing Volatile Organic Compounds (VOCs) and it seems that any plant will perform as well as others… This is important news – it means that any indoor room or office which is air-conditioned or closed for much of the time, can really benefit from having just one 200mm pot plant.”

A 1998 interview with Professor Burchett on the benefits of plants is also available online.

The new information on this issue is the filtering capacity of an individual plant in a room.  This is useful as workplaces will not need forests to assist in controlling the hazards presented by mechanical ventilation in modern buildings.  There are many reason, however, for having plants in workplaces.  Not only are they pleasant to see, they can also indicate a company’s green aims and credentials, particularly if in a more recent office block.

Let’s hope that the movement towards “safe design” for OHS purposes includes plants.

Kevin Jones

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